Meaning of ATONAL in English

ATONAL

a ‧ ton ‧ al /eɪˈtəʊn ə l, æ- $ -ˈtoʊ-/ BrE AmE adjective

a piece of music that is atonal is not based on a particular ↑ key 2 (4)

—atonality /ˌeɪtəʊˈnæləti, ˌeɪtəʊˈnælɪti, ˌæ- $ -toʊ-/ noun [uncountable]

Longman Dictionary of Contemporary English.      Longman - Словарь современного английского языка.